Method and apparatus for wireless transfer of chemical-mechanical planarization measurements

ABSTRACT

A method and apparatus for the wireless transfer of measurements made during chemical-mechanical planarization of semiconductor wafers with a planarizing machine. The apparatus includes a sensor connected to the semiconductor substrate or a movable portion of the planarizing machine. The apparatus further comprises a display spaced apart from the sensor and a wireless communication link coupled between the sensor and the display to transmit a signal from the sensor to the display. The wireless communication link may include an infrared link, a radio link, an acoustic link, or an inductive link. The sensor may measure force, pressure, temperature, pH, electrical resistance or other planarizing parameters. The sensor may also detect light reflected from a reflective surface of a substrate that is used to calibrate the planarizing machine.

TECHNICAL FIELD

[0001] The present invention relates to methods and devices for thewireless transfer of measurements made during chemical-mechanicalplanarization of semiconductor wafers.

BACKGROUND OF THE INVENTION

[0002] Chemical-mechanical planarization (“CMP”) processes removematerial from the surface of a semiconductor wafer in the production ofintegrated circuits. FIG. 1 schematically illustrates a CMP machine 10with a platen 20, a wafer carrier 30, a polishing pad 27, and aplanarizing liquid 28 on the polishing pad 27. The polishing pad 27 maybe a conventional polishing pad made from a continuous phase matrixmaterial (e.g., polyurethane), or it may be a new generation fixedabrasive polishing pad made from abrasive particles fixedly dispersed ina suspension medium. The planarizing liquid 28 may be a conventional CMPslurry with abrasive particles and chemicals that etch and/or oxidizethe wafer, or the planarizing liquid 28 may be a planarizing solutionwithout abrasive particles that contains only chemicals to etch and/oroxidize the surface of the wafer. In most CMP applications, conventionalCMP slurries are used on conventional polishing pads, and planarizingsolutions without abrasive particles are used on fixed abrasivepolishing pads.

[0003] The CMP machine 10 also has an underpad 25 attached to an uppersurface 22 of the platen 20 and the lower surface of the polishing pad27. In one type of CMP machine, a drive assembly 26 rotates the platen20 as indicated by arrow A. In another type of CMP machine, the driveassembly 26 reciprocates the platen 20 back and forth as indicated byarrow B. Since the polishing pad 27 is attached to the underpad 25, thepolishing pad 27 moves with the platen 20.

[0004] The wafer carrier 30 has a lower surface 33 to which a wafer 12may be attached, or the wafer 12 may be attached to a resilient pad 34positioned between the wafer 12 and the lower surface 33. The wafercarrier 30 may be a weighted, free-floating wafer carrier, or anactuator assembly 40 may be attached to the wafer carrier to impartaxial and/or rotational motion (indicated by arrows C and D,respectively).

[0005] To planarize the wafer 12 with the CMP machine 10, the wafercarrier 30 presses the wafer 12 face-downward against the polishing pad27. While the face of the wafer 12 presses against the polishing pad 27,at least one of the platen 20 or the wafer carrier 30 moves relative tothe other to move the wafer 12 across the planarizing surface 29. As theface of the wafer 12 moves across the planarizing surface 29, thepolishing pad 27 and the planarizing liquid 28 continually removematerial from the face of the wafer 12.

[0006] CMP processes must consistently and accurately produce a uniform,planar surface on the wafer to enable precise circuit and devicepatterns to be formed with photolithography techniques. As the densityof integrated circuits increases, it is often necessary to accuratelyfocus the critical dimensions of the photo-patterns to within atolerance of approximately 0.1 μm. Focusing photo-patterns of such smalltolerances, however, is difficult when the planarized surface of thewafer is not uniformly planar. Thus, CMP processes must create a highlyuniform, planar surface.

[0007] One problem with CMP processing is that the planarized surface ofthe wafer may not be sufficiently uniform across the whole surface ofthe wafer. The uniformity of the planarized surface is a function ofseveral variables, including the pressure between the wafer and theplanarizing surface, the temperature of the wafer and/or the planarizingsurface, and the temperature and pH of the planarizing liquid. Oneconventional approach to addressing this problem has been to measuresome or all of the above variables and adjust the CMP processingconditions to improve the uniformity of the wafers. This approach hascreated additional problems. For example, if the measurements are madewhile the CMP machine is stationary, they may not be representative ofthe actual conditions present during planarization. On the other hand,if sensors are placed on the wafer carrier to make measurements duringplanarization, mechanical means, such as slip rings and the like may berequired to transmit electrical signals from the moving sensors to astationary display.

[0008] One conventional approach for obtaining in situ measurements isto use remote sensing means. For example, an infrared gun may be used tomeasure the temperature of the wafer during planarization. This approachsuffers from several drawbacks. One drawback is that the temperaturereadings obtained from the infrared gun may be distorted by the presenceof the planarizing liquid. A second drawback is that remote sensingmeans may not be readily available for some types of sensors, forexample, pressure transducers. Accordingly, it may be difficult todetermine the pressure between the wafer and the polishing pad duringplanarization.

[0009] One conventional approach for obtaining in situ pressuremeasurements is to place the pressure transducer on a mechanical linkagebetween the wafer carrier and a fixed reference point. This approach maysuffer from still further drawbacks. For example, the weight of themechanical linkage may distort the pressure measurement, and the linkageitself may have such a high inertia that it is unable to respond quicklyto sudden pressure changes.

[0010] Still a further drawback with the foregoing conventionalapproaches is that each approach may require that a sensor andassociated peripheral hardware be installed on a large number of CMPmachines, although the planarizing characteristics may need to bemonitored only periodically. As a result, the cost for sensors,peripheral hardware, and maintenance may be higher than is necessary.

[0011] In the competitive semiconductor industry, it is also desirableto maximize the throughput of finished wafers. One factor that affectsthe throughput of CMP processing is the ability to accurately stopplanarizing a given wafer or type of wafers at a desired endpoint. Todetermine whether a wafer is at its desired endpoint, conventional CMPprocesses typically stop planarizing the wafer and measure the change inthickness of the wafer with an interferometer or other distancemeasuring device. If the wafer is under-planarized, CMP processing isresumed and the wafer is periodically measured until the wafer reachesits desired endpoint. If the wafer is over-planarized, the wafer may bepartially or fully damaged. The throughput of finished wafers isaccordingly greatly affected by the ability to accurately and quicklydetermine the endpoint of individual wafers and/or types of wafer.

SUMMARY OF THE INVENTION

[0012] The present invention is directed toward a method and apparatusfor the wireless transfer of measurements made duringchemical-mechanical planarization of a semiconductor substrate with aplanarizing device. The planarizing device may have a support, a platenassembly connected to the support, and a carrier movable relative to theplaten assembly and the support to remove material from a semiconductorsubstrate positioned between the carrier and the platen assembly. In oneembodiment, the apparatus may comprise a sensor connected to the platenassembly, the carrier, or the semiconductor substrate. The sensorgenerates a signal corresponding to a value of a selected property ofthe planarizing device or the semiconductor substrate. For example, theproperty may be a force exerted against the semiconductor substrate bythe carrier, a temperature or resistance of the semiconductor substrate,or the pH of planarizing liquid surrounding the semiconductor substrate.The apparatus may further include a display spaced apart from the sensorand a wireless communication link coupled between the sensor and thedisplay to transmit the signal from the sensor to the display. Thewireless communication link may include an infrared, radio, or acoustictransmitter and receiver, or a pair of inductors.

[0013] In one embodiment, the signal may be transmitted in real timefrom the sensor to the display. In another embodiment, the signal may bestored and then transmitted in a batch manner, and the communicationlink may include a cable or the wireless means described above. In stillanother embodiment, the apparatus may include a feedback loop thatchanges the selected property based on the signal generated by thesensor.

[0014] In yet another embodiment of the invention, the apparatus mayremove material from a substrate having a reflective layer and atransparent surface opposite the reflective layer. The apparatus mayinclude a light source positioned to illuminate the substrate, and alight sensor positioned to detect the presence or absence of lightreflected from the reflective layer through the transparent surface ofthe substrate. In a further aspect of this embodiment, the reflectivelayer may have a hardness approximately the same as the hardness of asemiconductor wafer so that removal of the reflective layer isrepresentative of semiconductor wafer planarization.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a partial cross-sectional elevation view of achemical-mechanical planarization machine in accordance with the priorart.

[0016]FIG. 2 is a partial cross-sectional elevation view of an apparatusin accordance with an embodiment of the present invention.

[0017]FIG. 3 is a top plan view of a portion of the apparatus shown inFIG. 2.

[0018]FIG. 4A is a block diagram of a transmitter assembly and areceiver assembly in accordance with an embodiment of the invention.

[0019]FIG. 4B is a block diagram of a transmitter assembly and areceiver assembly in accordance with another embodiment of theinvention.

[0020]FIG. 5 is a partial cross-sectional elevation view of a carrierassembly in accordance with another embodiment of the invention.

[0021]FIG. 6 is a partially schematic, partial cross-sectional elevationview of an apparatus in accordance with still another embodiment of theinvention.

[0022]FIG. 7 is a partial cross-sectional elevation view of a carrierassembly in accordance with yet another embodiment of the invention.

[0023]FIG. 8 is a partial cross-sectional elevation view of a portion ofan apparatus engaging a substrate in accordance with still anotherembodiment of the invention.

[0024]FIG. 9 is a top plan view of the substrate shown in FIG. 8.

[0025]FIG. 10 is a partial cross-sectional elevation view of a carrierassembly in accordance with another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention is directed toward methods and apparatusesfor transmitting data from a chemical-mechanical planarization machine.The apparatus may include a wireless communication link to transmit thedata from a movable portion of the machine to a fixed point. Manyspecific details of certain embodiments of the invention are set forthin the following description and in FIGS. 1-10 to provide a thoroughunderstanding of such embodiments. One skilled in the art, however, willunderstand that the present invention may have additional embodimentsand that they may be practiced without several of the details describedin the following description.

[0027]FIG. 2 illustrates a CMP apparatus 110 for measuring the values ofone or more parameters associated with chemical-mechanical planarizationof a semiconductor substrate or wafer 112. As discussed above withrespect to FIG. 1, the apparatus 110 has a platen 120, an underpad 125mounted to the top surface of the platen 120, and a polishing pad 127mounted to the top surface of the underpad 125. The platen 120 may bemovable relative to a fixed support structure 114 by means of a driveassembly 126 that may impart rotational motion (indicated by arrow A)and/or translational motion (indicated by arrow B) to the platen 120.

[0028] The apparatus 110 may also include a carrier assembly 130 thatengages the semiconductor substrate 112 and moves the semiconductorsubstrate relative to the polishing pad 127 to remove materialtherefrom. A retainer ring 131 prevents the semiconductor substrate 112from sliding away from the carrier assembly 130. The carrier assembly130 is supported relative to the polishing pad 127 by a horizontalsupport arm 143 and a vertical drive shaft 142. The horizontal supportarm 143 may include outer and inner telescoping segments 143 a and 143b. The outer telescoping segment 143 a is attached to the supportstructure 114, and the inner telescoping segment 143 b may sliderelative to the outer telescoping segment 143 a as indicated by arrow E,to oscillate the carrier assembly 130 in a horizontal direction. In oneembodiment, the inner telescoping segment 143 b and carrier assembly 130are driven by an actuator 140 a and a linkage 149, and in otherembodiments, other means oscillate the carrier assembly 130.

[0029] The drive shaft 142 extends between the inner telescoping segment143 b and the carrier assembly 130. The drive shaft 142 may be coupledto an actuator 140 b that imparts to the carrier assembly 130 a verticalmotion, indicated by arrow C, and/or a rotational motion, indicated byarrow D. The driveshaft 142 further includes a coupling member or plate144 that has a plurality of vacuum apertures 148 to releasably engagethe carrier assembly 130. The vacuum apertures 148 are coupled to avacuum source (not shown) by a series of connecting conduits 145 (shownin FIG. 2 as 145 a, 145 b, and 145 c) that pass through the drive shaft142 and the support arm 143. A rotational seal 146 at the junctionbetween the support arm 143 and the drive shaft 142 connects therotating portion of the conduit 145 a to the translating portions of theconduit 145 b and 145 c.

[0030] The carrier assembly 130 includes a mounting member or plate 150coupled to the coupling plate 144 and an engaging member or plate 132that engages the semiconductor substrate 112. The mounting plate 150 hasa smooth upper surface and an O-ring 154 to provide a gas-tight sealwith the coupling plate 144. When a vacuum is drawn through the vacuumapertures 148 by the vacuum source, the coupling plate 144 may flyengage the mounting plate 150.

[0031] The engaging plate 132 is positioned beneath the mounting plate150 and is coupled to the mounting plate 150 by a spacer ring 151 and avertical coupling 193. The spacer ring 151 is attached to a lowersurface of the mounting plate 150 and extends around the periphery ofthe mounting plate toward the engaging plate 132. The spacer ring 151has a plurality of circular apertures 152 in a lower flange 156 thereof.Bolts 153 extend through the apertures 152 and bear against the walls ofthe apertures to impart rotational motion from the drive shaft 142 tothe engaging plate 132. The lower flange 156 of the spacer ring 151 isspaced apart from the engaging plate 132 so that the spacer ring 151transmits no vertical force to the engaging plate 132. Instead, allvertical forces are transmitted to the engaging plate 132 and thesemiconductor substrate 112 through the vertical coupling 193.

[0032] In one embodiment, a force sensor 190 is positioned between thevertical coupling 193 and the mounting plate 150. In other embodiments,the force sensor 190 may be positioned in other portions of theapparatus 110, so long as it is in the load path between the actuator140 b and the semiconductor substrate 112, and is sufficiently close tothe semiconductor substrate 112 to accurately measure the verticalforces transmitted thereto. The force sensor 190 may be one of a varietyof commercially available transducers configured to measure steady stateand/or variable forces and generate a corresponding electrical signal. Acalibrator 194 may be attached to the mounting plate 150 and coupled tothe force sensor 190 to calibrate the electrical signal with a knownvalue.

[0033] The force sensor 190 is connected to a transmitter assembly 170that generates wireless signals corresponding to the force sensorsignals. The wireless signals are transmitted by a transmitter 177 toone or more transmitting transducers 175 and then to a receiver assembly160. The receiver assembly 160 includes a receiving transducer 161positioned to receive the wireless signals, and a receiver 165 coupledto the receiving transducer 161. The receiver assembly 160 is coupled toan electronic device 169. In one embodiment, shown in FIG. 2, theelectronic device 169 may include a display that displays the signals ina human readable format. In other embodiments, the electronic device 169may include a chart recorder, printer, or other output device. In stillfurther embodiments, the electronic device 169 may include otherdevices, such as a feedback device, as is discussed in greater detailbelow with reference to FIG. 6. In any case, the transmitter assembly170 and the receiver assembly 160 together form a wireless communicationlink between the force sensor 190 and the electronic device 169.

[0034]FIG. 3 is a top plan view of the mounting plate 150 and thetransmitter assembly 170 shown in FIG. 2. Referring to FIGS. 2 and 3,several transmitting transducers 175 are coupled to the transmitter 177with cables 192 routed through cable passages 155 in the mounting plate150. Accordingly, even where the signals emitted by the transmittingtransducers 175 travel in generally straight lines, the signals emittedby at least one of the transmitting transducers 175 will be coupled tothe receiving transducer 161 (FIG. 2) at all times.

[0035] The transmitting transducers 175 and the receiving transducer 161may transmit wireless signals by one or more of several means. Forexample, in one embodiment, the transmitting transducers 175 and thereceiving transducers 161 may generate and receive, respectively, opticsignals, such as infrared, ultraviolet, or visible light signals. In oneaspect of this embodiment, the transmitting transducer 175 can include alight source and a waveguide, such as a fiber optic cable, having anemission point from which optic signals are emitted. In otherembodiments, the transmitting transducer 175 may include other types ofwaveguides. In still further embodiments, the transmitting transducers175 and the receiving transducers 161 may generate and receive,respectively, radio signals or acoustic signals, for example, subsonic,sonic, or ultrasonic signals. In yet another embodiment, thetransmitting transducers 175 may include inductors that generatemagnetic signals and the receiving transducer 161 may include acorresponding inductor to receive the magnetic signal.

[0036] Returning to FIG. 2, the transmitting transducers 175 may bespaced apart from the receiving transducer 161 in each of the foregoingembodiments, and may be movable relative to the receiver assembly 160without interrupting the flow of signals therebetween. In the embodimentshown in FIG. 2, the transmitter assembly 170 may be attached to themounting plate 150. In other embodiments, the transmitter assembly 170may be attached to any portion of the apparatus 110 that moves relativeto the electronic device 169, such as the platen 120 or thesemiconductor substrate 112. The receiving transducer 161 may bepositioned adjacent the support structure 114, as shown in FIG. 2, or,as is also shown in FIG. 2, a receiving transducer 161 a may bepositioned on the platen 120 where the platen 120 does not move relativeto the electronic device 169. In still further embodiments, thereceiving transducer 161 may be positioned on any portion of theapparatus that is generally fixed relative to the electronic device 169.In any of the foregoing embodiments, the receiving transducer 161 mayinclude a parabolic horn to receive even relatively weak signalsgenerated by the transmitting transducer 175, reducing the powerrequired by the transmitter 177.

[0037]FIG. 4A is a schematic block diagram of a transmitter assembly 170and receiver assembly 160 in accordance with an embodiment of theinvention. The transmitter assembly 170 is configured to transmitsignals from several sensors 190 (shown as 190 a, 190 b, 190 c) that maybe calibrated with a corresponding plurality of calibrators 194 (shownas 194 a, 194 b, and 194 c). Each sensor 190 is coupled to a signalconditioner 171 (shown as 171 a, 171 b, and 171 c) to reduce noise inthe signals generated by the sensors 190. The conditioned signals arethen transmitted to a multiplexer 172, that samples each signal streamand compiles a single composite signal stream.

[0038] In one embodiment, the composite signal stream proceeds from themultiplexer 172 to a modulator 173 that modulates either the frequencyor the amplitude of the signal stream. In another embodiment, themodulator 173 may be replaced with an A/D processor 174, as shown indashed lines in FIG. 4A. The AID processor 174 may include a converter,a central processing unit or discrete logic device, a storage deviceand/or a control code unit, and transforms the analog signal from themultiplexer 172 to a bit stream which is then conveyed to thetransmitting transducer 175. The multiplexer 172, A/D processor 174, andtransducer 175 may comprise a commercially available unit, such as aMicrostamp system available from Micron Technology, Inc. of Boise, Id.,or a Strain Link™ system available from Microstrain of Burlington, Vt.

[0039] The transmitter assembly 170 further includes a power supply 178coupled to the sensors 190, the signal conditioners 171 and any othercomponents requiring power, such as the multiplexer 172, the modulator173, and the AID processor 174. In one embodiment, the power supply 178may include a battery. In another embodiment, the power supply mayinclude a solar cell or other device that does not require externalcable connections during planarization, for example, a first inductorthat is magnetically or electromagnetically coupled to a correspondingsecond inductor to generate electrical current.

[0040] The signal transmitted by the transmitting transducer 175 isreceived by the receiving transducer 161, as discussed above withreference to FIGS. 2 and 3. Where the signal is an analog signal, thereceiving transducer 161 is coupled to a demodulator 162 to convert thesignal to a voltage, then to a demultiplexer 163 to separate individualsignals from the signal stream, and then to a processor 164 a. Theprocessor 164 a may convert the voltage to a human readable format wherethe electronic device 169 is a display. Where the signal emitted by thetransmitting transducer 175 is a digital signal, the demodulator 162 anddemultiplexer 163 are replaced by a processor 164 b, as shown in dashedlines in FIG. 4A.

[0041] An advantage of the apparatus 110 shown in FIGS. 2-4A is that iteasily transmits force data from a rotating and translating portion ofthe apparatus to the fixed electronic device 169 without the need forslip rings or other mechanical devices. Accordingly, the apparatus 110may be less complex than conventional apparatuses and may be lesssusceptible to mechanical failure. Another advantage of the apparatus110 shown in FIGS. 2-4A is that it transmits real-time or nearlyreal-time force data because the communication link includes radio,infrared, or magnetic transmitters and receivers. As a result, thesignals are not delayed or otherwise hampered by mechanical linkages.This may be especially important for transmitting vibrationmeasurements, which may have such a high frequency that they are notaccurately transmitted by mechanical means.

[0042] Still another advantage of the apparatus 110 shown in FIGS. 2-3is that the carrier assembly 130 may be easily removed from theapparatus 110 and moved to another CMP machine. The receiver assembly160 and electronic device 169 may also be easily moved from one machineto another. Accordingly, the force sensor 190 may be used periodicallyto run diagnostic checks of individual CMP machines without the need tosimultaneously outfit each machine with a complete transmitter assembly170 and receiver assembly 160.

[0043]FIG. 4B is a schematic block diagram of a receiver assembly 160 aand a transmitter assembly 170 a in accordance with another embodimentof the invention. As shown in FIG. 4B, the receiver assembly 160 a isgenerally similar to the receiver assembly shown in FIGS. 2-4A. Thetransmitter assembly 170 a is generally similar to the transmitterassembly 170 shown in FIGS. 2-4A; however, it further includes a storageor memory device 179 coupled to the multiplexer 172. The storage device179 may be used to store data received from the sensors 190 and transmitthe data to the transducer 175 in a batch format. In one embodiment, forexample, the carrier assembly 130 (FIG. 2) may be halted prior toconveying the data from the sensor 190 to the electronic device 169. Inone aspect of this embodiment, the transducers 175 and 161 may bereplaced by a cable 166 that is coupled between the transmitter assembly170 a and the receiver assembly 160 a while the data is transmitted. Thecable 166 may be removed after the data has been transmitted and beforeresuming motion of the carrier assembly 130. An advantage of thetransmitter assembly 170 a shown in FIG. 4B when compared with thetransmitter assembly 170 shown in FIG. 4A is that it may eliminate theneed for the transducers 175 and 161. Conversely, an advantage of thetransmitter assembly 170 shown in FIG. 4A is that it is configured totransmit real-time data rather than batch data.

[0044]FIG. 5 is a partial cross-sectional elevation view of a carrierassembly 230 having sensors in accordance with another embodiment of theinvention. In addition to the force sensor 190 discussed above withreference to FIGS. 24B, the carrier assembly 230 may include temperaturesensors 290 (shown as 290 a and 290 b) and pH sensors 390 (shown as 390a and 390 b). One temperature sensor 290 a may include a conventionalthermocouple device that extends from the engaging plate 132 toward thepolishing pad 127 and/or the planarizing liquid 128 and is coupled tothe transmitter assembly 170 by leads 292 a. The other temperaturesensor 290 b may be integrated with a surface of the semiconductorsubstrate 112 to measure the temperature of the semiconductor substratedirectly, and may be coupled to the transmitter assembly 170 byconventional leads 292 b or by conventional leads in combination withvias in the structure of the semiconductor substrate 112.

[0045] The pH sensors 390 may include a conventional electronic pH metersuch as is available from PGC Scientific of Gaithersburg, Md., orBeckman Instruments of Fullerton, Calif. In one embodiment, shown inFIG. 5, one pH sensor 390 a may be attached to the carrier assembly 230.In another embodiment, also shown in FIG. 5, another pH sensor 390 b maybe attached to the platen 120, and may be coupled to a transmitter 177 band transmitting transducer 175 b, also attached to the platen 120. Instill further embodiments, the carrier assembly 230 and/or the platen120 may include other sensors to measure the values of other parametersrelated to CMP processes, so long as the measurements may be convertedto wireless signals.

[0046] An advantage of the temperature sensors 290 and the pH sensors390 shown in FIG. 5 is that they may be used to obtain additionaldiagnostic data during the planarization process. The signals generatedby the sensors may be transmitted in real-time, as is generally shown inFIG. 4A, or may be stored and transmitted in a batch fashion, as isshown in FIG. 4B. Data from different types of sensors (e.g., force,temperature, pH) and/or data from a plurality of sensors of the sametype (e.g., several force sensors) may be transmitted in a single datastream by using a multiplexer 172, as is generally shown in FIG. 4A.

[0047]FIG. 6 is a cross-sectional elevation view of an apparatus 410having an acoustic transmitting transducer 475, such as an audiospeaker, and an acoustic receiving transducer 461, such as an audiomicrophone, in accordance with another embodiment of the invention. Asshown in FIG. 6, the carrier assembly 430 includes a mounting member 450removably attached with bolts 447 to the coupling plate 444. Themounting member 450 includes a cylinder 437 having cylinder walls 436configured to slidably receive the engaging member 432. The engagingmember 432 includes an O-ring 438 that sealably engages the cylinderwalls 436 and is slidable within the cylinder 437 to press thesemiconductor substrate 112 into engagement with the polishing pad 127.The apparatus 410 further includes a pressurized air source 480 coupledwith conduits 445 a and 445 b to the cylinder 437. The air pressurewithin the cylinder 437 may be adjusted with the air source 480 to adesired level, thus establishing a desired force between thesemiconductor substrate 112 and the polishing pad 127.

[0048] As shown in FIG. 6, a pressure transducer 490 is configured tomeasure the air pressure within the cylinder 437 and transmit themeasurement to the transmitter assembly 170 and the acoustictransmitting transducer 475. The acoustic signal emitted by the acoustictransmitting transducer 475 is conveyed through the conduits 445 a and445 b to the acoustic receiving transducer 461 positioned at thepressurized air source 480. The acoustic receiving transducer 461 iscoupled to the receiver assembly 160 and the display 169, generally asdiscussed above with reference to FIGS. 24B. The receiver assembly 160may also be coupled to the pressurized air source 480 to provide afeedback loop. Accordingly, the receiver assembly 160 may be connectedto an electronic feedback device 469 to automatically control thepressurized air source 480, based on the signals received from theacoustic transmitting transducer 475, and provide a selected pressure inthe cylinder 437.

[0049] An advantage of the apparatus 410 shown in FIG. 6 is that it mayautomatically adjust the force between the semiconductor substrate 112and the polishing pad 127 based on measurements made by the pressuretransducer 490. In other embodiments, similar feedback loops may becoupled to a heater to regulate the temperature of the semiconductorsubstrate 112, or to a chemical dispenser to regulate the pH of theplanarizing solution 128 on the polishing pad 127. Another advantage ofan embodiment of the invention shown in FIG. 6 is that some existingplanarizing machines may include the air source 480 and the cylinder437, allowing the wireless communication link to incorporate existinghardware.

[0050]FIG. 7 is a cross-sectional elevation view of a carrier assembly530 having a light source 580 and a light detector, such as anelectronic light detector 590, in accordance with another embodiment ofthe invention. As shown in FIG. 7, the light source 580 may bepositioned in the mounting plate 550 above the engaging plate 532 todirect light through an aperture 535 in the engaging plate 532. Thelight passes through the aperture 535, through a transparent uppersurface of a transparent substrate 512, and strikes a reflective coating513 on the opposite side of the substrate 512. The reflected lightpasses back through the transparent upper surface of the substrate 512where it is detected by the light detector 590. The surface of thedetector 590 facing away from the substrate 512 may be shielded so thatthe detector receives reflected light rather than incident light. Whenthe reflective layer 513 is completely removed, light no longer reflectstherefrom, and the signal generated by the light detector 590 changes.

[0051] In one embodiment, the light source 580 generates visible lightand the light detector 590 detects visible light. In other embodiments,the light source 580 and detector 590 operate at other wavelengths. Inany case, signals generated by the detector 590 may be conveyed to thetransmitter assembly 170 and then to the receiver assembly 160 (FIG. 2),as was discussed above with reference to FIGS. 2-4B.

[0052] In one embodiment, the transparent substrate 512 may havedimensions generally similar to those of a conventional semiconductorsubstrate (such as a silicon substrate) and the reflective layer 513 mayhave a hardness that is representative of the surface of theconventional semiconductor substrate. When the transparent substrate 512is planarized, the reflective layer 513 may accordingly be removed at arate similar to the rate at which material is removed from aconventional semiconductor wafer surface. Accordingly, the carrierassembly 530 and transparent substrate 512 may be used to calibrate theapparatus 110 (FIG. 2) by simulating conditions under which an actualsemiconductor substrate is planarized.

[0053]FIG. 8 is a cross-sectional elevation view of an apparatus 610having a non-rotating light source 680 and light detector 690 inaccordance with another embodiment of the invention. As shown in FIG. 8,the light source 680 and the detector 690 are positioned above thecarrier assembly 630. Accordingly, the coupling plate 644, mountingplate 650, and engaging plate 632 are each provided with a plurality ofapertures 635 to allow the light generated by the light source 680 toilluminate the substrate 612 and reflect from the reflective layer 613upward to the detector 690, as was discussed above with reference toFIG. 7.

[0054]FIG. 9 is a top plan view of the substrate 612 shown in FIG. 8. Asshown in FIG. 9, the reflective layer 613 on the surface of thesubstrate 612 may include a plurality of radial segments 615, eachaligned with one or more of the apertures 635 (FIG. 8). Accordingly, anadvantage of the apparatus 610 and substrate 612 shown in FIGS. 8 and 9is that the light detector 690 may detect light reflected from a varietyof positions on the substrate 612 as the substrate rotates relative tothe light detector. This is advantageous because it may indicate areasof the substrate 612 that planarize at different rates.

[0055]FIG. 10 is a partial cross-sectional elevation view of a carrier730 and a substrate 712 in accordance with yet another embodiment of theinvention. In one aspect of this embodiment, the substrate 712 includesan electrically conductive layer 713 facing the polishing pad 127. Theconductive layer 713 is connected with leads 792 to an ohm meter 790that measures the resistance of the conductive layer 713. Duringplanarization, the thickness of the conductive layer 713 is graduallyreduced, altering the resistance of the conductive layer. The change inresistance is detected by the ohm meter 790, and may be used to indicatewhen planarization is complete or when various planarizing parameters,such as temperature and pressure, are either too great, creating toohigh a rate of planarization, or too small, creating too low a rate ofplanarization.

[0056] As shown in FIG. 10, the conductive leads 792 may connect to theplanarized surface of the substrate 712. In another embodiment, theconductive leads 792 may be coupled to vias that are integrally formedwith the substrate 712 and that extend between the leads 792 and theconductive layer 713. In still a further aspect of this embodiment, theconductive layer 713 may include the outer surface of a conventionalsemiconductor substrate.

[0057] From the foregoing it will be appreciated that, although specificembodiments of the invention have been described herein for purposes ofillustration, various modifications may be made without deviating fromthe spirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

1. An apparatus for transmitting signals from a planarizing device, theplanarizing device having a support, a platen assembly connected to thesupport, and a carrier movable relative to the platen assembly and thesupport to remove material from a semiconductor substrate positionedbetween the carrier and the platen assembly, the apparatus comprising: asensor connected to one of the platen assembly, the carrier, and thesemiconductor substrate, the sensor generating a signal corresponding toa value of a selected property of one of the planarizing device and thesemiconductor substrate; an electrical device spaced apart from thesensor; and a wireless communication link coupled between the sensor andthe display to transmit the signal from the sensor to the electricaldevice.
 2. The apparatus of claim 1 wherein the electrical deviceincludes a display.
 3. The apparatus of claim 1 wherein the electricaldevice includes a feedback device to change the value of the selectedproperty.
 4. The apparatus of claim 1 wherein the sensor includes aforce sensor.
 5. The apparatus of claim 4 wherein the carrier comprisesa mounting member removably coupled to the support and an engagingmember to engage the semiconductor substrate, the force sensor beingconnected between the mounting member and the engaging member to measurea force transmitted therebetween.
 6. The apparatus of claim 4 whereinthe force sensor includes a steady state force sensor.
 7. The apparatusof claim 4 wherein the force sensor is configured to measure a varyingforce.
 8. The apparatus of claim 1 wherein the sensor includes atemperature sensor.
 9. The apparatus of claim 1 wherein the platenassembly includes a platen and a quantity of planarizing liquid on asurface of the platen and the sensor includes a pH sensor positioned tomeasure a pH of the planarizing liquid.
 10. The apparatus of claim 1wherein the sensor is connected to the carrier.
 11. The apparatus ofclaim 1 wherein the sensor is connected to the semiconductor substrate.12. The apparatus of claim 11 wherein the sensor includes a thermocouplepositioned on a surface of the semiconductor substrate.
 13. Theapparatus of claim 11 wherein the semiconductor substrate has aconductive material on a surface thereof and the sensor includes an ohmmeter coupled to the conductive material to detect a change inresistance of the conductive material when a portion of the conductivematerial is removed during planarization of the semiconductor substrate.14. The apparatus of claim 1 wherein the platen assembly is movablerelative to the support and the sensor is attached to the platenassembly.
 15. The apparatus of claim 1 wherein the display is generallyfixed relative to the support.
 16. The apparatus of claim 1 wherein thecommunication link includes at least one optical transmitting transducerattached to one of the platen assembly and the carrier, thecommunication link further including an optical receiving transducerspaced apart from the optical transmitting transducer, the opticaltransmitting transducer moving relative to the optical receivingtransducer while the semiconductor substrate is planarized.
 17. Theapparatus of claim 1 wherein the communication link includes at leastone radio transmitting transducer attached to one of the platen assemblyand the carrier, the communication link further including a radioreceiving transducer spaced apart from the radio transmittingtransducer, the radio transmitting transducer moving relative to theradio receiving transducer while the semiconductor substrate isplanarized.
 18. The apparatus of claim 1 wherein the communication linkincludes at least one acoustic transmitting transducer attached to oneof the platen assembly and the carrier, the communication link furtherincluding an acoustic receiving transducer spaced apart from theacoustic transmitting transducer, the acoustic transmitting transducermoving relative to the acoustic receiving transducer while thesemiconductor substrate is planarized.
 19. The apparatus of claim 18 ,further comprising a conduit having first and second open ends andextending between the acoustic transmitting transducer and the acousticreceiving transducer, the acoustic transmitting transducer beingpositioned toward the first open end of the conduit and the acousticreceiving transducer being positioned toward the second open end of theconduit.
 20. The apparatus of claim 19 wherein the carrier has a plenumin fluid communication with the first open end of the conduit and theacoustic transmitting transducer is positioned in the plenum, theapparatus further comprising a pressurized air source coupled to thesecond open end of the conduit to supply air to the plenum and force thecarrier toward the platen.
 21. The apparatus of claim 1 wherein thecommunication link includes a first inductive coil attached to one ofthe platen assembly and the carrier, the communication link furtherincluding a second inductive coil spaced apart from the first inductivecoil, the first inductive coil moving relative to the second inductivecoil while the semiconductor substrate is planarized.
 22. The apparatusof claim 1 wherein the communication link includes a transmittingtransducer attached to one of the platen assembly and the carrier, thecommunication link further including a receiving transducer spaced apartfrom the transmitting transducer, the transmitting transducer beingmovable relative to the receiving transducer while the semiconductorsubstrate is planarized, further comprising a controller coupled to theplanarizing device to change the value of the selected property when thevalue differs from a selected value.
 23. The apparatus of claim 22wherein the selected property includes a force transmitted by thecarrier to the semiconductor substrate and the controller includes aforce controller coupled to the carrier to vary the force on thesemiconductor substrate.
 24. The apparatus of claim 22 wherein theselected property is a temperature of the semiconductor substrate andthe controller includes a temperature controller to vary the temperatureof the semiconductor substrate, the temperature controller being coupledto the receiver to change the temperature when the temperature differsfrom a selected value.
 25. The apparatus of claim 1 , further comprisinga power supply attached to the carrier and coupled to the sensor tosupply power thereto.
 26. The apparatus of claim 1 wherein the sensor isa first sensor, the signal is a first signal, and the selected propertyis a first selected property, further comprising: a second sensorattached to one of the platen assembly, the carrier, and thesemiconductor substrate, the second sensor generating a second signalcorresponding to a value of a second selected property; and amultiplexer coupled to the first and second sensors and thecommunication link to sequentially transmit the first and second signalsto the communication link.
 27. The apparatus of claim 1 wherein thecommunication link includes a plurality of wireless transmittingtransducers connected to the sensor and at least one wireless receiverspaced apart from the wireless transmitting transducers, the wirelesstransmitting transducers moving relative to the wireless receivingtransducer when the semiconductor substrate is planarized.
 28. Theapparatus of claim 1 wherein the signal is an analog signal and thecommunication link includes a wireless analog transmitting transducerand a wireless analog receiving transducer spaced apart from thewireless analog transmitting transducer.
 29. The apparatus of claim 1wherein the signal is a digital signal and the communication linkincludes a wireless digital transmitting transducer and a wirelessdigital receiving transducer spaced apart from the wireless digitaltransmitting transducer.
 30. The apparatus of claim 1 , furthercomprising a memory device coupled to the sensor to receive the sensorsignal and store the sensor signal for a selected period of time.
 31. Anapparatus for transmitting wireless signals from a planarizing device,the planarizing device having a support, a platen, and a carrier movablerelative to the support and the platen to planarize a semiconductorsubstrate engaged by the carrier as the carrier moves relative to theplaten, the apparatus comprising: a sensor coupled to one of the platen,the carrier and the semiconductor substrate to generate a sensor signalcorresponding to a value of a selected property of one of theplanarizing device and the semiconductor substrate; a wirelesstransmitter coupled to the sensor to receive the sensor signal andtransmit a wireless transmitter signal corresponding to the sensorsignal; and a wireless receiver spaced apart from the wirelesstransmitter to receive the transmitter signal, the wireless receiverbeing generally fixed relative to the support.
 32. The apparatus ofclaim 31 wherein the wireless transmitter includes a frequencymodulating transducer.
 33. The apparatus of claim 31 wherein thewireless transmitter includes an amplitude modulating transducer. 34.The apparatus of claim 31 wherein the sensor includes a force sensor.35. The apparatus of claim 31 wherein the sensor includes a temperaturesensor.
 36. The apparatus of claim 31 wherein the transmitter includesan optical transmitting transducer and the receiver includes an opticalreceiving transducer.
 37. The apparatus of claim 31 wherein thetransmitter includes a radio transmitting transducer and the receiverincludes a radio receiving transducer.
 38. The apparatus of claim 31wherein the transmitter includes an acoustic transmitting transducer andthe receiver includes an acoustic receiving transducer.
 39. Theapparatus of claim 38 wherein the acoustic transmitting transducerincludes an audio speaker.
 40. The apparatus of claim 38 wherein theacoustic receiving transducer includes an audio microphone.
 41. Theapparatus of claim 31 wherein the transmitter includes a first inductivecoil and the receiver includes a second inductive coil.
 42. Theapparatus of claim 31 wherein the sensor is a first sensor, the signalis a first signal, and the selected property is a first selectedproperty, further comprising: a second sensor attached to one of theplaten, the carrier, and the semiconductor substrate, the second sensorgenerating a second signal corresponding to a value of a second selectedproperty; and a multiplexer coupled to the first and second sensors andthe communication link to sequentially transmit the first and secondsignals to the wireless transmitter.
 43. The apparatus of claim 31 ,further comprising a memory device coupled to the sensor to receive thesensor signal and store the sensor signal for a selected period of time.44. An apparatus for storing data generated during planarization of asemiconductor substrate by a planarizing device, the planarizing devicehaving a support, a platen coupled to the support, and a carrier movablerelative to the platen to remove material from a semiconductor substratepositioned between the carrier and the platen, the apparatus comprising:a sensor coupled to the planarizing device to generate a sensor signalcorresponding to a value of a selected property of one of theplanarizing device and the semiconductor substrate; and a memory devicecoupled to the sensor to receive the sensor signal and store the sensorsignal.
 45. The apparatus of claim 33 , further comprising: an outputdevice; and a communication link operatively coupled between the memorydevice and the output device to transfer the signal from the memorydevice to the output device.
 46. The apparatus of claim 45 wherein thecommunication link comprises a cable coupled between the memory deviceand the output device.
 47. The apparatus of claim 45 wherein the outputdevice is selected from a display, a chart recorder and a printer. 48.The apparatus of claim 45 wherein the communication link includes awireless transmitter and a wireless receiver spaced apart from thewireless transmitter, the wireless transmitter moving relative to thewireless receiver while the semiconductor substrate is planarized. 49.The apparatus of claim 48 wherein the wireless transmitter includes anoptical transmitting transducer and the wireless receiver includes anoptical receiving transducer.
 50. The apparatus of claim 48 wherein thewireless transmitter includes a radio transmitting transducer and thewireless receiver includes a radio receiving transducer.
 51. Theapparatus of claim 48 wherein the sensor includes a force sensor. 52.The apparatus of claim 48 wherein the sensor includes a temperaturesensor.
 53. An apparatus for detecting removal of material from asubstrate, the substrate having a first surface and a second surfaceopposite the first surface, the substrate being light transmissive fromthe first surface to a point proximate the second surface, the secondsurface having a reflective layer attached thereto, the devicecomprising: a platen having a planarizing surface; a carrier having afirst surface and a second surface opposite the first surface, thesecond surface of the carrier being configured to receive the substrateand engage the substrate with the planarizing surface of the platen, thecarrier and substrate being movable relative to the platen when thesubstrate is engaged with the planarizing surface to remove thereflective layer from the substrate; a light source positioned proximateto the first surface of the substrate to irradiate the first surface;and a light sensor positioned proximate to the first surface of thesubstrate to detect light reflected from the reflective layer of thesubstrate through the first surface of the substrate.
 54. The apparatusof claim 53 wherein the light source emits visible light and the lightsensor detects visible light.
 55. The apparatus of claim 53 wherein thecarrier is fixed relative to the light source.
 56. The apparatus ofclaim 53 wherein the carrier is movable relative to the light source.57. The apparatus of claim 53 , further comprising the substrate whereinthe reflective layer of the substrate has a hardness approximately thesame as a hardness of a semiconductor wafer.
 58. The apparatus of claim53 , further comprising the substrate wherein the reflective layer ofthe substrate has a hardness approximately the same as a hardness of asilicon wafer.
 59. A method for transmitting data from a planarizingdevice having a first portion and a second portion movable relative tothe first portion to planarize a substrate positioned therebetween, themethod comprising: measuring a value of a selected property of one ofthe planarizing device and the substrate; generating a sensor signalcorresponding to the measured value; and transmitting the sensor signalfrom the second portion of the planarizing device with a wirelesscommunication link.
 60. The method of claim 59 , further comprisingreceiving the sensor signal at a position spaced apart from the secondportion of the planarizing device.
 61. The method of claim 59 whereinthe selected property is a temperature of the substrate and the act ofmeasuring a value includes measuring the temperature of the substrate.62. The method of claim 59 wherein the selected property is a forceexerted by at least part of the second portion of the planarizing deviceagainst the substrate and the act of measuring a value includesmeasuring the force.
 63. The method of claim 62 wherein the forceincludes a steady state component and a variable component and the actof measuring a value includes measuring the steady state component ofthe force.
 64. The method of claim 59 wherein the force includes asteady state component and a variable component and the act of measuringa value includes measuring the variable component of the force.
 65. Themethod of claim 59 wherein the substrate has a conductive portion, theselected property is a resistance of the conductive portion and the actof measuring a value includes measuring the resistance of the conductiveportion.
 66. The method of claim 59 wherein the planarizing deviceincludes a planarizing liquid in contact with the substrate duringplanarization of the substrate, the selected property includes a pH ofthe planarizing liquid, and the act of measuring a value includesmeasuring the pH of the planarizing liquid.
 67. The method of claim 59wherein the communication link includes a radio transmitting transducercoupled to the sensor and the act of transmitting the sensor signalincludes emitting a radio signal from the radio transmitting transducer,the radio signal corresponding to the sensor signal.
 68. The method ofclaim 59 wherein the communication link includes an optical transmittingtransducer coupled to the sensor and the act of transmitting the sensorsignal includes emitting an optical signal from the optical transmittingtransducer, the optical signal corresponding to the sensor signal. 69.The method of claim 59 wherein the communication link includes anacoustic transmitting transducer coupled to the sensor and the act oftransmitting the sensor signal includes emitting an acoustic signal fromthe acoustic transmitting transducer, the acoustic signal correspondingto the sensor signal.
 70. The method of claim 69 wherein the planarizingdevice includes a conduit having first and second open ends, theacoustic transmitting transducer being positioned toward the first openend of the conduit, and wherein the act of transmitting the sensorsignal includes transmitting the acoustic signal through the conduit.71. The method of claim 59 wherein the communication link includes aninductive coil attached to one of the carrier and the semiconductorsubstrate, and the act of transmitting the sensor signal includesgenerating an electromagnetic field with the inductive coil.
 72. Themethod of claim 59 wherein the act of transmitting the signal includestransmitting an analog signal.
 73. The method of claim 59 wherein theact of transmitting the signal includes transmitting a digital signal.74. The method of claim 59 , further comprising the act of changing thevalue of the selected property when the value differs from a selectedvalue.
 75. The method of claim 59 , further comprising storing thesignal for a selected period of time before transmitting the signal. 76.A method for transmitting data from a planarizing apparatus having afirst portion and a second portion movable relative to the first portionto planarize a semiconductor substrate positioned between the first andsecond portions, the method comprising: measuring a value of a selectedproperty of one of the planarizing apparatus and the semiconductorsubstrate and generating a sensor signal corresponding to the value ofthe selected property; storing the sensor signal in a memory device ofthe planarizing apparatus; and transmitting the sensor signal from thememory device.
 77. The method of claim 76 wherein the memory device isattached to the second portion of the planarizing apparatus, furthercomprising arresting motion of the second portion relative to the firstportion before transmitting the sensor signal.
 78. The method of claim77 wherein the act of transmitting the sensor signal includestransmitting the sensor signal over a cable coupled to the memorydevice.
 79. The method of claim 76 wherein the act of transmitting thesensor signal includes transmitting the sensor signal while the secondportion of the planarizing apparatus is moving relative to the firstportion.
 80. The method of claim 76 wherein the act of transmitting thesensor signal includes transmitting the sensor signal from an opticaltransmitting transducer to an optical receiving transducer spaced apartfrom the optical transmitting transducer.
 81. The method of claim 76wherein the act of transmitting the sensor signal includes transmittingthe sensor signal from a radio transmitting transducer to a radioreceiving transducer spaced apart from the radio transmittingtransducer.
 82. The method of claim 76 wherein the act of transmittingthe sensor signal includes transmitting the sensor signal from anacoustic transmitting transducer to an acoustic receiving transducerspaced apart from the acoustic transmitting transducer.
 83. The methodof claim 76 wherein the act of transmitting the sensor signal includestransmitting the sensor signal from a first inductive coil to a secondinductive coil spaced apart from the first inductive coil.
 84. A methodfor detecting removal of material from a substrate, the substrate havinga first surface and a second surface opposite the first surface, thesubstrate being light transmissive from the first surface to a pointproximate to the second surface, the second surface having a reflectivelayer attached thereto, the method comprising: removing at least aportion of the reflective layer; directing light through the firstsurface of the substrate and toward the reflective layer with a lightsource; and detecting light reflected by the reflective layer throughthe first surface of the substrate.
 85. The method of claim 84 whereinthe act of directing light includes directing visible light and the actof detecting light includes detecting visible light.
 86. The method ofclaim 84 , further comprising removing material from the reflectivelayer until light detected by the light sensor decreases from a firstselected value to a second selected value.
 87. The method of claim 84wherein the act of detecting light includes detecting light with anelectronic light sensor.